Control system



1933- F. c. BIGGERT, JR., ET'AL I 1,939,538

CONTROL SYSTEM Filed 001:. 2, 1931 Patented Dec. 12, 1933 CONTROL SYSTEMFlorence C. Biggert, Jr., Grafton, and Robert H. Ellis, Pittsburgh, Pa.,assignors to United Engineering & Foundry Company, Pittsburgh, Pa., acorporation of Pennsylvania Application October 2, 1931. Serial No.566,518 12 Claims. ((1164-68) This invention relates to a control systemand more particularly to an improved system for controlling theoperation of what is commonly knownin the metal working art as a flyingshear,

although as will be readily appreciated'from the following descriptionit may be utilized with various other devices having similar operatingcharacteristics.

In the cutting of moving stock by means of flying shears it is essentialin order to produce cuts of accurate lengths to drive the shears inpositive synchronism with the stock. To accomplish this end it has beenthe customary practice in the past to mechanically tie the drivingmechanism employed to operate the feeding means with that of the shears.Such. arrangements where any appreciable degree of flexibility of speedcontrol is demanded are exceedingly complicated and costly, as well asdiflicult to manufacture and maintain. In an effort to avoid thesedifliculties, various forms of electrically controlled drivingarrangements have been provided. These, however, as heretoforepracticed, although of simple construction and affording a more flexiblespeed control, as well as a satisfactory solution to many of thedifficulties common to the mechanical drives, have failed in theirprovisions of sufliciently positive and precise speed regulation betweenthe shears 80 and the stock, to meet with the demands of accuracy incutting required for many purposes.

With this in view, it is the primary object of this invention, generallystated, to provide an improved electrically controlled driving system 85for apparatus, such as flying shears, which is positive in operation,simple of construction and which incorporates the advantages of both theolder mechanical and previously practiced electrical drives without thedisadvantages of either.

A further object is to provide an electrically controlled drive forflying shears in which provision is made for starting the shears in amanner to control the amount of material cropped from the leading end ofthe stock as the stock it is started through the shear, and also insurethe first cut, as well as the succeeding cuts, being made when theshears are operating in positive synchronism with the stock.

Another object is to provide an electrically controlled and operativedrive which is capable of absorbing the shock produced when the shearblades engage the moving stock as the cut is made and for doing sowithout injury to the driving elements.

These and numerous other objects, as well as the various otheradvantages andnovel features of the invention, will be apparent when thefollowing detailed description is read in conjunction with theaccompanying drawings, wherein the single figure shown illustrates whatis now considered the preferred embodiment of the invention.

Referring to the drawing a common form of shear arrangement is shownwhich comprises a shear 1, a piece of stock 2, and a set of pinch rolls3 for feeding the stock continuously through the shears. In place of thepinch rolls any other suitable work feeding device, such as a rollingmill may be substituted, and as shown here may be coupled directly to adriving motor 4 by means of a drive shaft 5 to receive its operatingpower.

In accordance with this invention shear 1 may be any of a number of wellknown forms of shears, for example, a drum type shear in which theknives mounted thereon are adapted to come into cutting engagement onintermittent revolutions of the drums or with every revolution thereof,or it may be a revolving blade form of shear equipped with a drivingconnection for adjusting the cutting speed of the blades independentlyof the overall rotary speed or other forms which are adapted to beoperated from a constant or uniform main source of power supply. Withsuch shears the lengths of the cuts are determined by the relativespeeds of the feeding mechanisms and the shears 86 and for accuracy incuts there must be no departure from the speed relation between the two.

In addition to cutting the stock into lengths of accurate size anotherrequirement which is imposed upon flying shears such as are con- 90,templated by this invention is that they must include a provision forcontrolling the amount of crop end removed from the forward end of eachpiece of stock. To accomplish this the shears must be provided withmeans for varying their 5 speed between pieces of stock or they must bestopped and restarted during such intervals. In accordance with thelatter form of operation the cutting blades must be in a suitableposition relative to the leading end of the stock as it advances towardthem and a reasonable control over the starting of the shears must beprovided. This requires that the shears be stopped in a definiteposition after they complete their opm5 eration on each piece of stockand that they be restarted as the leading end of the succeeding piece ofstock arrives at a definite point in advance of the shears. Also thatthe shears be accelerated rapidly to the exact cutting speed 110suitable to the desired length of out before the cut is made.

The mass and corresponding inertia of flying shears and their associatedparts are usually large and the-desired starting time from rest tocutting speed is usually small; hence, a high starting torque isrequired for acceleration. When the shears are once running at constantspeed however, they require but comparatively low torque, but it isessential, as stated above, in order to produce accurate cuts that theirspeed relation to the stock be maintained absolutely constant.

With this in view, a motor 6 having a high starting torque and in whichthe torque de-- power to start the shear in the manner desired.

is also provided with sufficient power to overcome the friction of theshear and do the work of cutting at cutting speeds with some power inreserve. Preferably, it is a series type direct current motor or devicehaving the characteristics of such motors, and in addition. to meetingsuch demands, is capable of doing so over quite a wide range of speed.The speed may be varied by simply inserting a variable resistance in thepower circuit and thus avoid a speed change gear connection forvariation of speed.

To provide for maintaining the speed relation between the shear andstock constant so as to insure accurate cutting, a synchronous machine'7 which is normally adapted to function as a motor and which has apull-out torque in excess of the torque which motor 6 is capable ofdeveloping at cutting speeds, is also coupled to shear 1. For supplyingalternating current to this motor which is synchronized with the speedof the stock or for electrically coupling it for synchronized actionswith the stock feeding mechanism another synchronous machine 8isemployed being electrically connected to machine '1 by a circuitconsisting of conductors 9 and 11. This latter machine while normallyadapted to function as a generator is provided with the same or similarpull-out and load characteristics as 'machine '7, and to insure itsoperating in positive synchronism with pinch rolls 3, it is connectedthrough a speed change gear unit 12 and gears 13 and 14 directly to thedrive shaft 5 of motor 4, the latterrmotor having sufficient capacity tosupply the power demands of machine 8.

In the preferred operation of the system, machine 7 i is adjusted tofunction as a motor and to carry a small portion of the friction loadimposed on the shear and is adapted to be electric'ally connectedv tomachine 8 during the starting of the shear before motor 6 completelyaccelerates the shear up to cuttingspeed. In this way, machine 7 assiststo some extent'in the acceleration of the shear and because of its highpull-out'torque prevents motor 6 exceeding the shear speed selected fora predetermined length of cut and also insures the speed of the shearbeing maintained in synchronism with that of the stock. Foraccomplishing such a result, machine 8 and speed change gear unit 12 maybe considered as speed regulators and machine 7 .ment with switch 22when both motor 6 and maby means of the speed change gear unit 12.

As illustrated in the drawing a source of current supply provided bysupply mains Li and La may be employed for operating both motors 4 and6, these motors, being connected thereto by conductors 15 and 16, and 17and 18, respectively. To increase the speed control over the system avariable resistor '19 may be connected in the supply circuit of motor 4.For automatically starting and stopping the shear,'a pair of flagswitches 21 and 22 are connected in parallel circuit relation to eachother in the circuit of motor 6, for example, as in conductor 1'1, andare adjustably positioned in the path of travel of the stock in thefront and rear, respectively, of the shear.

With such an arrangement, as soon as the leading end of stock 2 engagesflag switch 21, motor 6 is energized to set the shear in motion. Ifdesired, machine 7 may be started at the same instant by employing amagnetic contactor 23 for closing the circuit, connecting machines 8 and,7 and placing the actuating coil of this contactor across motor 6 asshown, or in any other suitable position where it will be controlled byswitches 21 and 22. As another altematlve, a ,centrifugal switch 24 maybe coupled to machine 7 and its contacts connected in shunt relationwith switch 23, the governor of the switch being adjusted to 1 close thecircuit at any speed desired. 11 such provision is made, a hand switch25 may be inserted in the circuit of switch 23 and opened in case thecentrifugal switch 24 is employed. Also in such case a magnetic switch20 may be inserted in series with switch 24 and adapted as shown toclose with switch 21 and open with switch 22. Either type of control,however, will be adapted to set machine 7 in operation before the cut ismade, and, preferably, for a purpose which will presently appear beforecutting speed is reached. Under such conditions this motor functions toassist in the drive of the shear. Although if the speed of the shearexceeds the speed desired i when machine 7 is energized, the" latterinstead of functioning as a motor will function as a generator. n thelatter occurs, it sends its generated power back to shaft-5 by causingmachine 8 to function as a motor and at the same time maintains shear 1in synchronism with rolls 3.

When the trailing end of the stock passes switch 21, it will fall open.However, motor 6 and machine '1 will be maintained in operation untilsuch. end of the stock passes out of engageshaft of motor 6 with itsoperating coil connected in series with that motor. In this way 14b thebrake is automatically released when motor 6 isenergized and appliedwhen it is deenergized.

It will be appreciated of course that other and more positive actingmeans of well'known form may be employed for positively positioning theblades each time the shear is stopped; that the switches 21 and 22 mayhave their position altered for different speeds of operation and that are sistor 27 as referred to above may be employed to vary the speed ofmotor 6 to accord with any speed selected by changing gear unit 12 whichselection determines the lengths of the cuts.

Another feature of this invention resides in its ability to relieve theshear of deleterious shocks at the instant of cutting. In flying shears,as is known, the time of cutting is very short and during such timequite heavy loads are imposed upon the shear parts. If the speed of theshear is rigidly maintained during this period, these heavy strains aretransmitted throughout the driving mechanism, as is the case in a directand complete mechanical drive, and greatly reduces the life of such adrive. If, however, the speed of the shear be permitted to retardslightly during the cutting instant, the kinetic energy of the shearparts assists in performing the cut and the stresses in the mechanismare greatly reduced.

It is characteristic of a synchronous motor that when it is driving aload the rotor lags its field by some part of a phase angle, and whenbeing driven as a generator it leads its field by some part of a phaseangle. In fact this lag or lead may amount to percent of a pole pitch.This permits an oscillation of a portion of a pole pitch when themachine is changed from motor to generator operation where the torquesvary from positive to negative value. In accordance with this inventionthis characteristic of machine 7 is employed to advantage in making itpossible to utilize the kinetic energy of the shear parts to assist inperforming the cuts, it being appreciated that motor 6 also permits ofsuch performance. To best employ such feature the proper selection ofpole pitch and gear ratio between motor 7 and shear 1 is selected toprovide the speed drop neeessary to take advantage of the kinetic energyof the shear parts to supply the cutting forces, and by such selection,as will be understood, machine 7 may be operated continuously as eithera motor or a generator, or as both. After the cut is completed thecombined torques of motors 6 and 7 will be available to reestablish thetrue running speed of the shear and by properly proportioning the loadson the motors there will be no jump- -g of poles and the exact shearrotation per minute will be maintained.

According to the provisions of the patent statutes, we have explainedthe principle and mode of operation of our invention and haveillustrated and described what we now consider to be its bestembodiment. However, we desire ,to have it understood that within thescope of the appended claims, the invention may be practiced otherwisethan as specifically illustrated and described.

We claim: 1

1. The combination with a work machine of the type subjected to suddenimpacts in. operation which is adapted to operate upon moving stock, ofmeans for feeding stock to said machine, a driving motor'operablycoupled to the work machine which is adapted to start it from restindependently of said feeding means and rapidly accelerate to operatingspeed, an electro-synchronous machine coupled to said work machine forpositively controlling its operating sred, and a secondelectro-synchronous machine iven in synchronism with said feedingmechanism and electrically coupled to said first mentioned synchronousmachine whereby ,positive synchronous operation is maintained betweensaid stock feeding means and said work machine..

2. The combination with a flying shear of a driving motor having acomparatively high starting torque operably coupled thereto, and anelectro-synchronous machine also coupled to said shear for controllingits operating speed.

3. The combination with a flying shear of a driving motor having arelatively high starting torque, which decreases as its speed increases,operably coupled to said shear for rapidly accelerating and driving it,an electro-synchronous machine positively coupled to the shear, andmeans for supplying alternating current of a given frequency to saidsynchronous machine to control the operating speed of the shear.

4. The combination of a flying shear having a series type direct currentmotor and a synchronous motor both operably coupled thereto, said seriesmotor being adapted to carry the major portion of the shear load and toaccelerate it from rest to operating speed in a relatively short periodof time and said synchronous motoradapted to positively control theoperating speed of the shear.

5. The combination of a flying shear having a variable speed motoroperably coupled thereto for supplying its operating power, asynchronous machine coupled to it for positively controlling its cuttingspeed, and means for selectively connecting a source of synchronouspower to said synchronous machine.

6. The combination with a flying shear of means for feeding stock tosaid shear, a driving motor having a relatively high starting torque forstarting said shear from rest and accelerating it to cutting speed in arelatively short period of time, a synchronous machine coupled to saidshear to control its cutting speed, means for automatically energizingsaid driving motor as the leading end of a piece of stock is fed to theshear, and means for automatically energizing said synchronous machinebefore the first cut is made.

7. The combination with a flying shear of means for feeding stock tosaid shear, a variable speed motor having a comparatively high startingtorque coupled to said shear for starting and operating it, anelectro-synchronous machine, having a pull-out torque in excess of thefull speed torque of said motor, positively coupled to said shear, asecond motor positively coupled to said stock feeding means, a secondelectrosynchronous machine positively coupled to said stock feedingmeans, and means for electrically connecting said electro-synchronousmachines together to provide positive synchronous operation between theshear and the stock feeding means.

8. The combination with a flying shear of means for feeding stock tosaid shear, a variable speed motor having a comparatively high startingtorque coupled to said shear for rapidly accelerating and operating it,an electro-synchronous machine positively coupled to the shear forcontrolling its speed, a second motor positively coupled to said stockfeeding means, a second electro-synchronous machine also positivelycoupled to said stock feeding means, a flag switch 'for starting saidfirst mentioned motor and arranged to be operated by the advancing endof a piece of stock before it reaches the shears, and means forautomatically electrically connecting said electro-synchronous machinestogether before the first cut is made to provide synchronous operationbetween said shear and stock.

9. The combination with a flying shear of means for feeding stock tosaid shear, a variable speed ing motor, a flag switch adjustablyarranged in the path of the stock in front of said shear and connectedto start said first mentioned motor when the leading end of the stockengages the flag, means arranged to be operated automatically toelectrically connect said synchronous machines together before the firstcut is made whereby to provide positive synchronous action between theshear and stock and thereby insure accurate lengths of cut, and a secondflag switch arranged to maintain the shear in operation untilthetrailing end of the stock has passed a predetermined point.

10. The combination with a flying shear of means for feeding stock tosaid shear, a variable speed motor having a comparatively high startingtorque coupled to said shear for accelerating it from rest at a rapidspeed and supplying it with operating power, an electro-synchronousmachine positively coupled to said shear, a driving motor 'coupled tosaid stock feeding means, a second electro-synchronous machine coupledto said driving motor, a flag switch adjustably arranged in the path ofthe stock in front of said shear and connected to start saidjirstmentioned motor when the leading end of the stock engages the 1 flag,means arranged to be operated automatically to electrically connect saidsynchronous machines together before the first cut is made whereby toprovide positive synchronous action between the shear and stock toinsure accurate lengths of cut, a second flag switch arranged tomaintain the shear in operation until the trailing end of the stock haspassed a predetermined point, and means for'stopping the shear atsubstantially the same point in its cycle of operation each time it isstopped.

11. The combination with a flying shear of means of feeding stock to it,a variable speed motor having a comparatively high starting torquecoupled to said shear, means for varying the speed and startingcharacteristics of said motor, an electro-synchronous machine positivelycoupled to said shear, a driving motor positively coupled to said stockfeeding means, a second electro-synchronous machine positively coupledthrough a speed change gear unit to said driving motor, and means forelectrically coupling said electro-synchronous machines together whensaid shear is operated whereby to maintain the speed of said shear inpositive synchronism with said stock feeding means and at aspeed'relative thereto determined by the setting of said speed changegear unit. I

12. The combination with a flying shear of a direct current motor forstarting and operating said shear, a synchronous motor positivelycoupled to the shear for controlling its speed, means for continuouslyfeeding stock through the shear, a motor connected to positively operatesaid feeding means, a synchronous generator positively coupled to bedriven in synchronism with said feed mechanism, and means forelectrically con-- necting saidsynchronous motor to receive current fromsaid synchronous generator and thereby maintain the speed of said shearin positive synchronism with that of said stock.

FLORENCE C. BIGGERT, JR. ROBERT H. ELLIS.

